JP5862658B2 - Receiving circuit and filtering method thereof - Google Patents

Description

[Description of related applications]
The present invention is based on the priority claim of Japanese Patent Application No. 2011-066944 (filed on Mar. 28, 2011), the entire contents of which are incorporated herein by reference. Shall.
The present invention relates to a receiving circuit and a filtering method, and more particularly to a receiving circuit corresponding to a plurality of wireless standards and a filtering method thereof.

  2. Description of the Related Art In recent years, wireless integrated circuits (Integrated Circuits: IC) such as digital terrestrial television broadcasting and wireless LAN (Local Area Network) are mounted on mobile terminals. The carrier frequency of digital terrestrial television broadcasting is 862 MHz or less, the signal bandwidth is 8 MHz, the carrier frequency of wireless LAN is 5 GHz or less, the signal bandwidth is 40 MHz or less, and most of the major wireless standards are carrier frequencies of 5 GHz or less. The bandwidth is 100 MHz or less. On the other hand, for realization of higher-speed wireless communication, UWB (Ultra Wideband) using a maximum carrier frequency of 10 GHz and a signal bandwidth of 500 MHz or more, and WirelessHD (using a carrier frequency of 60 GHz and a signal bandwidth of several GHz or more) Researches such as Wireless High Definition) and WiGig (Wireless Gigabit) are being conducted. In the future, it is desired to realize a wireless IC capable of supporting these multiple standards with a single chip.

  Currently, for wireless standards having a carrier frequency of 5 GHz or less and a signal bandwidth of 100 MHz or less, support for multiple standards is in progress (for example, Non-Patent Documents 1 and 2). On the other hand, for communication standards using ultra-wideband such as UWB and millimeter wave, the frequency of signals handled is high, making it difficult to deal with general-purpose circuits. Therefore, in order to realize a receiving IC that can cope with a radio standard using ultra-wideband such as UWB in addition to digital terrestrial television broadcasting and wireless LAN, a plurality of signal processing systems are juxtaposed as shown in FIG. The configuration is realistic.

  The receiving apparatus in FIG. 11 includes a first receiving system 110a that handles a specific ultra-wideband wireless standard and a second receiving system 110b that handles major wireless standards such as a wireless LAN. The first reception system 110a is, for example, a reception system dedicated to UWB, and a band used in UWB is selected in advance by a band selection filter outside the IC. The second receiving system 110b is a general-purpose receiving system capable of complying with a radio standard such as a carrier frequency of 5 GHz or less and a signal bandwidth of 100 MHz or less. Is selected by a band selection filter.

  In the first reception system 110a, a radio frequency (RF) signal is input to a low noise amplifier (LNA) 103a in the IC via an antenna 101a and a band selection filter 102a. In the subsequent mixers 104a and 104b, quadrature demodulation is performed simultaneously with frequency conversion to baseband (BB), and further in channel selection filters 105a and 105b and variable gain amplifiers (VGA) 106a and 106b, respectively. Signal processing such as filtering and amplitude adjustment is performed. Thereafter, the signals are converted into digital signals by analog-to-digital converters (ADCs) 107 a and 107 b, and various digital processes are performed by the digital baseband unit 109.

  On the other hand, the second receiving system 110b is different from the first receiving system 110a in that the RF filter 108 is inserted after the LNA 103b. This is because interference signals other than the band used in UWB, for example, have been removed in advance in the first reception system 110a, while various carrier wave frequencies of, for example, 5 GHz or less are present in the second reception system 110b. This is due to the input of a signal. That is, in order to avoid interference in the circuit at the subsequent stage, the RF filter 108 that passes only a signal having a desired carrier frequency is required.

  As described above, a plurality of signal processing systems and the like are juxtaposed to constitute a receiving apparatus, so that a plurality of wireless standards can be handled relatively easily.

  Relatedly, Patent Document 1 discloses an intermediate frequency generation method for a radio unit in a TDMA communication method or a TDD communication method. In this intermediate frequency generation method, a first mixer based on a first local frequency signal is provided on one side of a bandpass filter common to transmission and reception, and a second mixer based on a second local frequency signal is provided on the other side. On the other hand, a third mixer based on the second local frequency signal is provided on the other side of the common bandpass filter, and a fourth mixer based on the first local frequency signal is provided on one side, and the third mixer Is configured to mix the same frequency signal as the second local frequency signal and the second intermediate frequency signal, and the transmission signal is transmitted between the common bandpass filter and the fourth mixer as the first intermediate frequency. A quadrature modulator that modulates the signal is inserted.

JP-A-7-273682

V. Giannini, et al. "A 2mm2 0.1-to-5GHz SDR Receiver in 45nm Digital CMOS," ISSCC Dig. Tech. Papers, pp. 408-409, Feb. 2009. S. Lerstaveesin, et al. "A 48-860 MHz CMOS Low-IF Direct-Conversion DTV Tuner," IEEE J. et al. Solid-State Circuits, vol. 43, no. 9, pp. 2013-2024, Sep. 2008.

  The following analysis is given in the present invention.

  However, the conventional receiving apparatus has a problem that the area of the circuit is increased and the cost is increased. That is, in the receiving circuit integrated in the IC, there are three types of channel selection filters 105a and 105b for the first reception system, RF filter 108 for the second reception system, and channel selection filters 105c and 105d. is necessary. In general, the filter circuit uses a large number of passive elements such as capacitors, which increases the area. The area is not negligible with respect to the area of the entire receiving apparatus. An object of the present invention is to provide a small-area receiving circuit and a filtering method therefor.

A receiving circuit according to one aspect of the present invention is output by a first mixer that converts the frequency of a first signal having a first frequency input from the outside and outputs the first signal, and the first mixer. A first selector that selects either a signal or an externally input second signal having a second frequency different from the first frequency, and selected by the first selector A filter that removes a predetermined frequency band of the signal; and a second selector that selects an output to the outside of the signal from which the frequency band has been removed or an output to a subsequent circuit .

A receiving circuit according to another aspect of the present invention includes a first mixer that frequency-converts and outputs a first component of a first signal having a first frequency input from the outside, and a first mixer A second mixer that frequency-converts and outputs a second component of the signal, and a first component of the first signal subjected to frequency conversion, or a first component that is input from the outside and is different from the first frequency. A first selector that selects one of the second signals having the second frequency, and a second selector that selects either the second component of the frequency-converted first signal or the second signal. A first filter for removing the first frequency band of the signal selected by the first selector, and a second filter for removing the second frequency band of the signal selected by the second selector. and second filter, the first signal frequency band is removed, to the outside A third selector that selects an output or an output to a subsequent circuit; and a fourth selector that selects an output to the outside of the signal from which the second frequency band has been removed or an output to the subsequent circuit. And a selector .

A filtering method according to another aspect of the present invention is a signal filtering method in a receiving circuit, and is a first filtering method obtained by frequency-converting a signal that is input from the outside and that has a first frequency. Selecting either a signal or a second signal that is input from outside and is a second frequency different from the first frequency, and removing a predetermined frequency band of the selected signal ; The signal from which the frequency band has been removed is selected to be output to the outside or frequency-converted and output to the outside .

  According to the present invention, the chip area can be reduced.

The figure which shows the structure of the receiving circuit of the 1st Embodiment of this invention. 1 is a circuit diagram showing an example of a mixer according to a first embodiment of the present invention. The circuit diagram which shows the other example of the mixer of the 1st Embodiment of this invention. The circuit diagram which shows an example of the selector of the 1st Embodiment of this invention. FIG. 3 is a circuit diagram illustrating an example of a filter according to the first embodiment of the present invention. The figure which shows the structure of the receiving circuit of the 2nd Embodiment of this invention. The figure which shows the structure of the receiving circuit of the 3rd Embodiment of this invention. The figure which shows the structure of the receiving circuit of the 4th Embodiment of this invention. The figure which shows the structure of the receiving circuit of the 5th Embodiment of this invention. The figure which shows the structure of the receiver circuit of the 6th Embodiment of this invention. The figure which shows the structure of the conventional receiver corresponding to multiple radio | wireless standards.

  Hereinafter, an embodiment for carrying out the present invention will be outlined. Note that the reference numerals of the drawings attached to the following outline are only examples for facilitating understanding, and are not intended to be limited to the illustrated embodiments.

  A receiving circuit according to an embodiment of the present invention includes a first mixer (10 in FIG. 1) that converts a frequency of a first signal having a first frequency input from the outside and outputs the first signal, and a first mixer The first selector (11 in FIG. 1) that selects either the signal output by the second signal or the second signal having the second frequency input from the outside, and selected by the first selector A filter (12 in FIG. 1) for removing a predetermined frequency band of the signal, and a second selector (FIG. 1) for selecting an output to the outside of the signal from which the frequency band has been removed or an output to a subsequent circuit. 13) and a second mixer (14 in FIG. 1), which is a circuit at a subsequent stage, that converts the frequency of the signal output by the second selector and outputs the second signal. Equal to the carrier frequency.

  In the receiving circuit, the filter may function as an input side and an output side for the first and second selectors, respectively.

  In the receiving circuit, the frequency band may be determined according to whether the signal selected by the first selector is the frequency-converted first signal or second signal.

  A receiving circuit according to another embodiment of the present invention includes a first mixer (60 in FIG. 6) that frequency-converts and outputs a first component of a first signal having a first frequency input from the outside. A second mixer (61 in FIG. 6) for frequency-converting and outputting the second component of the first signal, and the first component of the frequency-converted first signal or the first component input from the outside A first selector (62 in FIG. 6) that selects any one of the second signals having two frequencies, and either the second component of the frequency-converted first signal or the second signal A second selector for selecting one (63 in FIG. 6), a first filter for removing the first frequency band of the signal selected by the first selector (64 in FIG. 6), and a second A second filter (65 in FIG. 6) for removing a second frequency band of the signal selected by the selector of the first, A third selector (66 in FIG. 6) for selecting an output to the outside of the signal from which the frequency band has been removed or an output to a subsequent circuit, and an external of the signal from which the second frequency band has been removed The fourth selector (67 in FIG. 6) that selects the output to the output or the circuit to the subsequent stage, and the frequency output from the signal output by the third selector or the signal output by the fourth selector A third mixer (68 in FIG. 6) and a fourth mixer (69 in FIG. 6), which are subsequent circuits to be converted, are provided.

  In the receiving circuit, the first frequency band is determined according to whether the signal selected by the first selector is the signal output from the first mixer or the second signal. May be determined according to whether the signal selected by the second selector is the signal output from the second mixer or the second signal.

  In the receiving circuit, a third filter (70 in FIG. 7) for removing the third frequency band of the signal output from the third mixer (68 in FIG. 7) and a fourth mixer (69 in FIG. 7) are provided. You may make it further provide the 4th filter (71 of FIG. 7) which removes the 4th frequency band of the signal to output.

  The receiving circuit further includes a first switch (80 in FIG. 8) that allows the second signal to be input to the third mixer and the fourth mixer. The frequency conversion may be performed on any of the two signals, the signal output by the third selector, and the signal output by the fourth selector.

  In the receiving circuit, either the signal output from the first mixer (60 in FIG. 9) or the signal output from the third mixer (68 in FIG. 9) is input to the third filter (70 in FIG. 9). The fifth selector (90 in FIG. 9) to be enabled and the signal output from the second mixer (61 in FIG. 9) or the signal output from the fourth mixer (69 in FIG. 9) You may make it further provide the 6th selector (91 of FIG. 9) which enables input to a 4th filter (71 of FIG. 9).

  In the receiving circuit, the second selector (63a in FIG. 10) is any one of the second component of the first signal subjected to frequency conversion, the second signal, and the signal output by the first filter. Such a signal may be selected.

  According to such a receiving circuit, the chip area can be reduced by combining the channel selection filter of the first receiving system and the RF filter of the second receiving system in the conventional configuration into one. In addition, by adopting a reception method in which frequency conversion is performed a plurality of times in accordance with the corresponding wireless standard, the frequency of the local oscillator can be lowered and power consumption of the drive circuit and the like can be suppressed.

  Next, some embodiments of the present invention will be described in detail with reference to the drawings. Note that in all the drawings described below, the same components are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

[First Embodiment]
FIG. 1 shows a configuration of a receiving circuit according to the first embodiment of the present invention. The receiving circuit of the present embodiment includes a mixer 10 that frequency-converts and outputs a first signal IN1 having a first frequency input from the outside, and a signal output by the mixer 10 or a second signal input from the outside. A selector 11 that selects any one of the second signals IN2 of the frequency of the signal, a filter 12 that removes a predetermined frequency band of the signal selected by the selector 11, and an external of the signal from which the frequency band has been removed A selector 13 that selects either the output to the signal OUT1 or the output to the mixer 14; and the mixer 14 that converts the frequency of the signal output by the selector 13 and outputs the signal OUT2. The mixer 10 corresponds to the first mixer, the selector 11 corresponds to the first selector, the selector 13 corresponds to the second selector, and the mixer 14 corresponds to the second mixer.

  Hereinafter, the operation of the receiving circuit of this embodiment will be described using specific numerical values.

  First, a case where a radio signal having a signal bandwidth of 100 MHz or more, such as UWB, is received as the first signal IN1. The signal bandwidth of UWB is 528 MHz. The reception method is a direct conversion method in which an RF signal is directly converted into a baseband, and the pass bandwidth of the filter 12 is 264 MHz, which is half of the signal bandwidth. The selector 11 selects a signal output from the mixer 10, and the selector 13 is set to select the output as the signal OUT1 to the outside. The input UWB signal IN 1 is frequency-converted by the mixer 10 and input to the filter 12 via the selector 11. The filter 12 operates as a channel selection filter and suppresses interference waves of adjacent channels. The filter 12 outputs only the desired channel signal to the outside as the signal OUT1 through the selector 13.

  Next, an operation when a radio signal having a signal bandwidth of 100 MHz or less, such as terrestrial digital television broadcasting, is received as the second signal IN2. Here, consider a case where the carrier frequency is 230 MHz and the passband width is 8 MHz. As in the case of UWB, the reception method is the direct conversion method, and the pass bandwidth of the filter 12 is 264 MHz as described above. The selector 11 selects the second signal IN2, and the selector 13 is set to select the output to the mixer 14. The input digital terrestrial television broadcast signal is input to the filter 12 via the selector 11. The filter 12 operates as an RF filter that selects only a signal having a predetermined carrier frequency, and outputs a desired signal to the mixer 14 via the selector 13. In this numerical example, the band of the filter 12 is wide with respect to the carrier frequency. However, in the RF filter, it is not necessary to suppress even a disturbing signal close to the carrier frequency, and such a shift is not a problem. At the subsequent stage of the filter 12, the desired signal is frequency-converted by the mixer 14 and then output to the outside as the signal OUT2.

  In the above operation example, the filter 12 serves as both a channel selection filter in the UWB receiver and an RF filter in the receiver for digital terrestrial television broadcasting. Can be grouped into pieces. That is, an effect that the chip area can be suppressed as compared with the conventional case is obtained.

  Furthermore, the receiving circuit according to the present embodiment can support not only the direct conversion method but also a dual conversion method in which frequency conversion is performed twice. The operation of the dual conversion method will be described taking as an example a case where a wireless LAN signal having a carrier frequency of 4980 MHz and a signal bandwidth of 20 MHz is received as the first signal IN1. During the operation of the dual conversion method, the selector 11 selects the signal from the mixer 10 and the selector 13 is set to select the output to the mixer 14. The input wireless LAN signal is input to the mixer 10 as the first signal IN1, frequency-converted to an intermediate frequency band, and input to the filter 12 via the selector 11. Here, the mixer 10 mixes the 4980 MHz RF signal and the 4716 (= 4980-264) MHz local oscillation signal, and outputs a signal having an intermediate frequency of 264 MHz. In the subsequent filter 12, interference signals other than those in the intermediate frequency band are suppressed. Note that the interference signal positioned at 5244 (= 4980 + 264) MHz corresponding to the image frequency with respect to the desired signal of 4980 MHz is sufficiently suppressed by an external filter in advance, so there is no problem of interference. The signal output from the filter 12 is output to the mixer 14 via the selector 13, and is frequency-converted from the intermediate frequency to the baseband by the mixer 14, and then output to the outside as the signal OUT2.

  In the dual conversion method described above, the frequency of the local oscillation signal used in the mixer 10 can be suppressed lower than that in the direct conversion method. Therefore, the power consumption of the drive circuit that operates at the local oscillation frequency of the mixer 10 can be suppressed. On the other hand, since the local oscillation frequency used in the mixer 14 is equal to the intermediate frequency and is sufficiently lower than the carrier frequency, the power consumption of the drive circuit operating at the local oscillation frequency in the mixer 14 can be ignored. Therefore, by using the dual conversion method, it is possible to suppress the power consumption of the entire receiving apparatus as compared with the direct conversion method.

  In addition, the receiving circuit of the present embodiment can perform frequency conversion by a digital circuit and perform only interference wave removal. Such an operation will be described by taking as an example the case of receiving a terrestrial digital audio broadcast signal having a carrier frequency of 90 MHz and a signal bandwidth of 430 kHz as the second signal IN2. In this example, it is desirable that the band of the filter 12 be 90 MHz, but there is no problem even if it is wider than that depending on the dynamic range and sampling frequency of the subsequent circuit. At this time, the selector 11 selects the second signal IN2, and the selector 13 is set to select the output to the outside as the signal OUT1. The input digital terrestrial audio broadcast signal is input to the filter 12 via the selector 11 as the second signal IN2. In the filter 12, unnecessary interference signals are suppressed. The signal output from the filter 12 is output to the outside via the selector 13 as the signal OUT1. Thereafter, the 90 MHz band radio signal is converted from an analog signal to a digital signal and subjected to various data processing such as demodulation.

  In the method described above, the filter 12 functions as an anti-aliasing filter that removes an interference signal having a frequency equal to or higher than the Nyquist band of the analog-digital converter in the subsequent stage. Further, processing such as frequency conversion, interference signal removal, and amplitude adjustment are all performed by digital signal processing, and these processing can be performed with higher accuracy than when analog processing is performed. Furthermore, when the processing can be updated by software, the signal processing content can be flexibly changed. In other words, this method can flexibly cope with a plurality of wireless standards having relatively low radio frequencies.

  Note that numerical values such as the carrier frequency, the signal bandwidth, the filter pass bandwidth, and the intermediate frequency are not necessarily the above-described values.

  The filter 12 is preferably a variable filter whose bandwidth is variable depending on whether the signal input from the selector 11 is the first signal IN1 or the second signal IN2. In addition, a variable filter that can change characteristics such as a low-pass type, a band-pass type, a high-pass type, and a band elimination type according to the corresponding wireless standard and communication environment may be used.

  Furthermore, the operation examples of the direct conversion method and the dual conversion method have been described here. However, the present invention is not limited to these, and can be applied to other reception systems such as a low intermediate frequency system using a local oscillation frequency slightly different from the carrier frequency.

  Further, it is preferable to select the intermediate frequency so that the ratio between the local oscillation frequency in the mixer 10 and the local oscillation frequency in the mixer 14 becomes an integer during operation in the dual conversion system. Thus, the local oscillation signals of the mixer 10 and the mixer 14 can be easily generated by performing integer division based on a single local oscillation signal. In particular, the ratio between the local oscillation frequency in the mixer 10 and the local oscillation frequency in the mixer 14 is preferably a power of two. Furthermore, 1: 2 or 1: 4 is optimal. Thereby, since a simple divide-by-2 can be used, the circuit configuration can be greatly simplified.

  Next, the mixers 10 and 14 will be described. One specific circuit example of the mixers 10 and 14 in this embodiment is shown in FIG. In FIG. 2, the mixer 10 (14) includes NMOS transistors Q1 to Q6 and resistance elements R1 and R2. The NMOS transistors Q3 and Q4 have a differential pair in which the sources are commonly connected to the drain of the NMOS transistor Q1, the gates are connected to the port B, and the drains are connected to the power supply via the resistance elements R1 and R2. Configure. The NMOS transistors Q5 and Q6 have their sources connected in common to the drain of the NMOS transistor Q2, their gates connected to the port B in reverse phase, and their drains connected to the power supply via the resistance elements R1 and R2. Configure a differential pair. The drains of the NMOS transistors Q3 and Q5 commonly serve as one end of the port C, and the drains of the NMOS transistors Q4 and Q6 commonly serve as the other end of the port C. MOS transistors Q1 and Q2 have their sources grounded and their respective gates connected to port A.

  The mixer 10 (14) having such a configuration is called a Gilbert cell mixer that mixes the differential signals of the ports A and B and outputs them as differential signals to the port C, and is generally used in an RF circuit. The received RF signal and the local oscillation signal are differentially input to ports A and B, respectively, and the baseband signal is differentially output from port C.

  Next, another circuit example of the mixers 10 and 14 is shown in FIG. In FIG. 3, the mixer 10 (14) includes NMOS transistors Q11 to Q14. The NMOS transistor Q11 has a source connected to one end of the port A, a gate connected to one end of the port B, and a drain connected to one end of the port C. The NMOS transistor Q12 has a source connected to the other end of the port A, a gate connected to one end of the port B, and a drain connected to the other end of the port C. The NMOS transistor Q13 has a source connected to the other end of the port A, a gate connected to the other end of the port B, and a drain connected to one end of the port C. The NMOS transistor Q14 has a source connected to one end of the port A, a gate connected to the other end of the port B, and a drain connected to the other end of the port C.

  The mixer 10 (14) having such a configuration is a passive mixer that mixes the differential signals of the ports A (C) and B and outputs the mixed signals to the port C (A) as a differential signal. It has the advantage of high linearity. Here, the input or output signals of ports A, B, and C are the same as those in FIG.

  Next, the selectors 11 and 13 will be described. A specific circuit example of the selectors 11 and 13 in this embodiment is shown in FIG. In FIG. 4, the selector 11 (13) includes an inverting element (inverter) INV and transfer gates TG1 and TG2 using NMOS transistors and PMOS transistors, and shows only one of a pair corresponding to a differential signal. The other has the same configuration.

  The transfer gate TG1 includes an NMOS transistor Q21 and a PMOS transistor Q22 that connect drains and sources in common. The sources of the NMOS transistor Q21 and the PMOS transistor Q22 are connected to the port A1, and the respective drains are connected to the port B1. The transfer gate TG2 includes an NMOS transistor Q23 and a PMOS transistor Q24 that connect drains and sources in common. The sources of the NMOS transistor Q23 and the PMOS transistor Q24 are connected to the port A0, and the respective drains are connected to the port B1. The gates of the NMOS transistor Q21 and the PMOS transistor Q24 are connected to the port C1, and the gates of the PMOS transistor Q22 and the NMOS transistor Q23 are connected to the output of the inverting element INV that inverts the logical value of the port C1.

  In the selector 11 (13) having the above configuration, when the voltage of the port C1 is at a low level, the transfer gate TG1 is in a conductive state, the transfer gate TG2 is in an open state, and the port A0 and the port B1 are connected. Short circuit. On the other hand, when the voltage at the port C1 is high, the transfer gate TG1 is opened, the transfer gate TG2 is turned on, and the port A1 and the port B1 are short-circuited.

  Such a selector 11 (13) is provided corresponding to each differential signal. In addition, when it is necessary to operate the selector 11 (13) so that neither of the ports A0 and A1 is selected, a logic circuit (not shown) for controlling the transfer gates TG1 and TG2 to be simultaneously opened is added. To be configured. Further, if three or more sets of transfer gates are arranged and controlled by different signals, it is possible to configure a selector that selects one path from three or more paths.

  Next, the filter 12 will be described. A specific circuit example of the filter 12 in this embodiment is shown in FIG. The filter 12 is an active filter including operational amplifiers OP1 and OP2, capacitive elements C2 to C5, and resistive elements R6 to R13.

  In the operational amplifier OP1, a capacitive element C2 and a resistive element R9 are connected in parallel between the non-inverting output terminal and the non-inverting input terminal, and a capacitive element C3 and a resistive element R10 are connected in parallel between the inverting output terminal and the inverting input terminal. The non-inverting input terminal is connected to one end of the input port IN through the resistance element R6, and the inverting input terminal is connected to the other end of the input port IN through the resistance element R7. The operational amplifier OP2 has a capacitive element C4 connected between the non-inverting output terminal and the non-inverting input terminal, a capacitive element C5 connected between the inverting output terminal and the inverting input terminal, and the non-inverting input terminal connected to the resistance element. R12 is connected to the inverting output terminal of the operational amplifier OP1, the inverting input terminal is connected to the non-inverting output terminal of the operational amplifier OP1 via the resistor element R13, and the non-inverting output terminal is connected to the operational amplifier OP8 via the resistor element R8. The non-inverting input terminal of OP1 is connected, the inverting output terminal is connected to the inverting input terminal of the operational amplifier OP1 through the resistance element R11, and the non-inverting output terminal and the inverting output terminal are respectively connected to one end and the other end of the output port OUT. Connecting.

  The filter 12 having such a configuration is a second-order low-pass filter that passes the low-frequency of the differential signal of the input port IN and outputs the differential signal to the output port OUT. By controlling the value, the pass bandwidth can be changed. In addition, a Gm-C filter using a voltage-current converter and a capacitor, an LC filter using an inductor and a capacitor element, and the like can be used. In any case, the pass band width can be changed by controlling the element values (voltage-current conversion gain, inductance, capacitance value).

[Second Embodiment]
FIG. 6 shows a configuration of a receiving circuit according to the second embodiment of the present invention. The receiving circuit of the present embodiment includes a mixer 60 that converts the frequency of the first component of the first signal IN1 having the first frequency input from the outside, and outputs the second component of the first signal as the frequency. A mixer 61 that converts and outputs, and a selector 62 that selects either the first component of the first signal IN1 subjected to frequency conversion or the second signal IN2 of the second frequency input from the outside. And a selector 63 for selecting either the first component of the frequency-converted first signal or the second signal, and the first frequency band of the signal selected by the selector 62 is removed. The filter 64, the filter 65 for removing the second frequency band of the signal selected by the selector 63, and the output of the signal from which the first frequency band has been removed to the outside as a signal OUT1, or to the subsequent circuit Select the output of The selector 66, the selector 67 for selecting the output to the outside as the signal OUT3 or the output to the subsequent circuit of the signal from which the second frequency band has been removed, and the signals output by the selectors 66 and 67 Are provided with mixers 68 and 69, which are subsequent circuits. Mixers 68 and 69 output signals OUT2 and OUT4 to the outside, respectively.

  Here, the mixers 60, 61, 68, and 69 correspond to the first, second, third, and fourth mixers, respectively, and the selectors 62, 63, 66, and 67 correspond to the first, second, and second mixers, respectively. 3 and 4 correspond to the selectors, and the filters 64 and 65 correspond to the first and second filters, respectively. The stop bands of the filters 64 and 65 correspond to the first and second frequency bands, respectively.

  In the receiving circuit of this embodiment, the mixers 60 and 61 perform orthogonal demodulation simultaneously with frequency conversion by using local oscillation signals whose frequencies are equal to each other and whose phases are different from each other by 90 degrees. A baseband signal of a Q-phase (Quadrature-phase) component is obtained as the (In-phase) component and the second component. Similarly, in the mixers 68 and 69, by performing orthogonal demodulation simultaneously with frequency conversion, I-phase and Q-phase baseband signals are obtained as signals OUT2 and OUT4.

  Further, when receiving the second signal IN2, both the filters 64 and 65 can be used in parallel, or only one of them can be used. Specifically, if both the selectors 62 and 63 select the second signal IN2, and both the selectors 66 and 67 select the output to the mixers 68 and 69, the filters 64 and 65 are arranged in parallel. In other words, the noise is lower than when only one of the filters is used. If the selectors 63 and 67 are opened in this state, only the filter 64 is used, and the circuit of the filter 65 can be shut off. That is, power consumption can be suppressed as compared to the case where both filters are used.

  Further, when the first signal IN1 is received by the double conversion method, the mixers 60 and 61 perform frequency conversion to the intermediate frequency without performing quadrature demodulation, and the mixers 68 and 69 perform the intermediate frequency simultaneously with the quadrature demodulation. To baseband frequency conversion. At this time, the selectors 62 and 63 select the outputs from the mixers 60 and 61, respectively, and the selectors 66 and 67 set so as to select the outputs to the mixers 68 and 69, respectively. The mixers 60 and 61 use a common local oscillation signal, and the mixers 68 and 69 use local oscillation signals whose phases are different from each other by 90 degrees. Thus, I-phase and Q-phase baseband signals are obtained as the signals OUT2 and OUT4 as the outputs of the mixers 68 and 69.

  The filters 64 and 65 are preferably variable filters whose bandwidth is variable depending on whether the input signal is the first signal IN1 or the second signal IN2. In addition, a variable filter that can change characteristics such as a low-pass type, a band-pass type, a high-pass type, and a band elimination type according to the corresponding wireless standard and communication environment may be used.

  Furthermore, the operation examples of the direct conversion method and the dual conversion method have been described here. However, the present invention is not limited to this, and can be applied to other reception systems such as a low intermediate frequency system using a local oscillation frequency slightly different from the carrier frequency.

  In addition, it is preferable to select the intermediate frequency so that the ratio of the local oscillation frequency in the mixers 60 and 61 and the local oscillation frequency in the mixers 68 and 69 becomes an integer when operating in the dual conversion system. Thus, the local oscillation signals of the mixers 68 and 69 and the mixers 68 and 69 can be easily generated by performing integer division based on a single local oscillation signal. Furthermore, the ratio of the local oscillation frequency in the mixers 60 and 61 and the local oscillation frequency in the mixers 68 and 69 is preferably a power of 2. In particular, 1: 2 or 1: 4 is optimal. Thereby, since a simple divide-by-2 can be used, the circuit configuration can be greatly simplified.

[Third Embodiment]
FIG. 7 shows a configuration of a receiving circuit according to the third embodiment of the present invention. The receiving circuit of this embodiment is different from the receiving circuit of the second embodiment in that filters 70 and 71 are added after the mixers 68 and 69, respectively. The filters 70 and 71 correspond to the third and fourth filters, respectively, and the stop bands of the filters 70 and 71 correspond to the third and fourth frequency bands, respectively. In the receiving circuit of the present embodiment, for example, when the first signal IN1 is received, channels are selected by the filters 64 and 65, and when the second signal IN2 is received, the interference waves are removed by the filters 64 and 65. Channel selection can be performed at 70 and 71. Similarly, in the dual conversion method, channels can be selected by the filters 70 and 71.

  In the mixers 68 and 69, in the case of a low intermediate frequency reception method that performs frequency conversion to a low intermediate frequency instead of the baseband, the filters 70 and 71 are complex bands that can suppress the image signal. A path filter may be used.

[Fourth Embodiment]
FIG. 8 shows the configuration of a receiving circuit according to the fourth embodiment of the present invention. The receiving circuit of this embodiment is different from the receiving circuit of the second embodiment in that a switch 80 is added to the path through which the second signal IN2 is input to the mixers 68 and 69. Here, the switch 80 corresponds to the first switch. Further, the mixer 68 converts the frequency of the signal selected by the selector 66 or the second signal IN2 input via the switch 80, and the mixer 69 converts the signal selected by the selector 67 or the switch 80. The frequency of the second signal IN2 input via the signal is converted.

  The receiving circuit of this embodiment can simultaneously receive both the first signal IN1 and the second signal IN2. That is, the selectors 62 and 63 are set so as to select the signals of the mixers 60 and 61, respectively, the selectors 66 and 67 select the output to the outside, and the switch 80 is in the conductive state. At this time, the I-phase component of the first signal IN1 is output to the outside as the signal OUT1 via the mixer 60, the selector 62, the filter 64, and the selector 66, and the Q-phase component of the first signal IN1 is 61, the selector 63, the filter 65, and the selector 67 are output to the outside as the signal OUT3. On the other hand, the I-phase component of the second signal IN2 is output to the outside as the signal OUT2 via the switch 80 and the mixer 68, and the Q-phase component of the second signal IN2 is output via the switch 80 and the mixer 69. The signal is output to the outside as the signal OUT4. With the above operation, basebands of I phase and Q phase can be obtained for each of the first and second signals IN1 and IN2. That is, simultaneous reception can be performed for a plurality of wireless standards such as UWB and digital terrestrial broadcasting.

  However, since there is no RF filter in the reception path of the second signal IN2, the carrier frequency and the local oscillation signal frequency of the mixers 68 and 69 are selected so that interference in the circuits after the mixers 68 and 69 does not become a problem. Is limited. For example, the interference signal located at the harmonic of the carrier frequency is previously removed by a band selection filter outside the chip.

  The operation when the switch 80 is in the open state is the same as in the second embodiment.

[Fifth Embodiment]
FIG. 9 shows a configuration of a receiving circuit according to the fifth embodiment of the present invention. As compared with the third embodiment, the receiving circuit of the present embodiment includes a selector 90 that selects and outputs either the output of the mixer 60 or the output of the mixer 68, and the output of the mixer 61. The difference is that a selector 91 that selects and outputs one of the 69 outputs is added. The selectors 90 and 91 correspond to the fifth and sixth selectors, respectively.

  The operation of the receiving circuit of this embodiment will be described below. The selectors 62 and 63 select the second signal IN2, or are opened for any path, and the selectors 90 and 91 are set to select the outputs of the mixers 60 and 61, respectively. At this time, the first signal IN1 is frequency-converted to baseband by the mixers 60 and 61 and simultaneously subjected to quadrature demodulation, and then output to the filters 70 and 71 via the selectors 90 and 91, respectively, for channel selection. The signals OUT2 and OUT4 are output to the outside. The receiving circuit of the present embodiment is effective when the carrier frequency is high but the signal bandwidth is narrow, and the power consumption is suppressed by cutting off the unused circuits of the filters 64 and 65 and the mixers 68 and 69. be able to.

  Here, the operation when the selectors 90 and 91 select the outputs of the mixers 68 and 69 is the same as that of the third embodiment.

[Sixth Embodiment]
FIG. 10 shows a configuration of a receiving circuit according to the sixth embodiment of the present invention. The receiving circuit of this embodiment is different from the second embodiment in that the selector 63 is replaced with a selector 63a. The selector 63 a selects any one of the three signals of the output of the mixer 61, the second signal IN 2, and the output of the filter 64 and outputs the selected signal to the filter 65. In the receiving circuit of this embodiment, when receiving the second signal IN2, the selector 62 selects the second signal IN2, the selector 66 is opened, the selector 63a is connected to the output of the filter 64, The selector 67 is set to be connected to the mixers 68 and 69. As a result, the filters 64 and 65 are connected in cascade, so that the filter order is doubled and a steeper cutoff characteristic can be obtained. That is, even under conditions where a larger disturbance signal exists, the interference signal can be sufficiently suppressed and only the desired signal can be received.

  Further, if the selector 62 selects the output of the mixer 60, the selector 66 is opened, and the selector 63a is connected to the output of the filter 64, the first signal IN1 can also be received. However, since quadrature demodulation cannot be performed by the mixers 60 and 61, a dual conversion method in which the selector 67 selects the output to the mixers 68 and 69 and the mixers 68 and 69 perform quadrature demodulation is adopted. Alternatively, the selector 67 needs to select an output to the outside and perform quadrature demodulation externally.

  The operation when the selector 63a selects the mixer 61 or the second signal IN2 is the same as that of the second embodiment.

  It should be noted that the disclosures of the aforementioned patent documents and the like are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) can be combined or selected within the scope of the claims of the present invention. . That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

10, 14, 60, 61, 68, 69 Mixer 11, 13, 62, 63, 63a, 66, 67, 90, 91 Selector 12, 64, 65, 70, 71 Filter 80 Switch C2-C5 Capacitance element INV Inverting elements OP1, OP2 Operational amplifiers Q1-Q6, Q11-Q14, Q21, Q23 NMOS transistors Q22, Q24 PMOS transistors R1, R2, R6-R13 Resistance elements TG1, TG2 Transfer gates

Claims (10)

A first mixer for frequency-converting and outputting a first signal including a first frequency input from the outside;
A first selector that selects one of the signal output from the first mixer or the second signal that is input from the outside and includes a second frequency different from the first frequency; ,
A filter for removing a predetermined frequency band of the signal selected by the first selector;
A second selector that selects an output to the outside of the signal from which the frequency band has been removed, or an output to a subsequent circuit;
A receiving circuit comprising: Before SL filter, a receiving circuit according to claim 1 wherein said the first and second selector, characterized by functioning as a respective input and output sides.   The frequency band is determined according to whether the signal selected by the first selector is the frequency-converted first signal or the second signal. The receiving circuit according to 1 or 2. A first mixer for frequency-converting and outputting a first component of a first signal including a first frequency input from the outside;
A second mixer for frequency-converting and outputting a second component of the first signal;
A first component of the frequency-converted first signal or a second signal that is input from the outside and includes a second frequency different from the first frequency. 1 selector,
A second selector that selects either the second component of the first signal that has undergone the frequency conversion or the second signal;
A first filter for removing a first frequency band of the signal selected by the first selector;
A second filter for removing a second frequency band of the signal selected by the second selector;
A third selector that selects an output to the outside of the signal from which the first frequency band has been removed, or an output to a subsequent circuit;
A fourth selector for selecting an output to the outside of the signal from which the second frequency band has been removed, or an output to the subsequent circuit;
A receiving circuit comprising: The first frequency band is determined according to whether the signal selected by the first selector is a signal output from the first mixer or the second signal,
The second frequency band is determined according to whether the signal selected by the second selector is a signal output from the second mixer or the second signal. The receiving circuit according to claim 4. Converts the frequency of the output signal by pre-Symbol third output by the selector signal or the fourth selector, the third mixer and a fourth mixer is a circuit of the subsequent stage,
A third filter for removing a third frequency band of the signal output from the third mixer;
A fourth filter for removing a fourth frequency band of the signal output from the fourth mixer;
The receiving circuit according to claim 4, further comprising: A fifth selector that allows enter one hand signal the signal or said third mixer the first mixer is output is output to the third filter,
A sixth selector that allows either the signal output from the second mixer or the signal output from the fourth mixer to be input to the fourth filter;
The receiving circuit according to claim 6, further comprising: A first switch that allows the second signal to be input to the third mixer and the fourth mixer;
The third mixer and the fourth mixer are any one of the second signal, a signal output by the third selector, and a signal output by the fourth selector. receiving circuit according to claim 6 or 7, characterized in that frequency conversion.   The second selector selects any one of the second component of the frequency-converted first signal, the second signal, and the signal output by the first filter. The receiving circuit according to any one of claims 4 to 8, wherein: A signal filtering method in a receiving circuit, comprising:
A first signal obtained by frequency conversion of a signal that is input from the outside and having a frequency of the first frequency, or a second signal that is input from the outside and that is a second frequency that is different from the first frequency Select one of the signals
Removing a predetermined frequency band of the selected signal ;
A filtering method, wherein the signal from which the frequency band has been removed is selected to be output to the outside or frequency-converted and output to the outside .

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